This invention relates to an electrostatographic printing machine and more particularly concerns an automatic measurement of a cleaning brush nip width for process control and/or diagnostics.
One of the significant factors in the performance of a cleaning brush is the number of brush fiber tips which are available to contact toner entering the zone formed by the interference of the brush to the photoreceptor. The higher the number of available fibers (fiber strikes) to clean, the better the cleaning and the more robust the cleaner will be to stress inputs and environments. Fiber strikes are a function of the brush diameter, brush speed and brush to photoreceptor interference (i.e. BPI). At any point in time only the speeds and interference can be varied. Over time, however, the diameter of the brush will shrink with usage. This is due to the mechanical set of the brush fibers due to repeated compression in the photoreceptor nip and, if present, detoning roll or flicker bar interferences. Additionally, the brush diameter will decrease due to the accumulation of toner within the brush. (Toner accumulated near the core of the brush holds the fibers in deflected positions.)
Verification of the interference of a new brush to a photoreceptor or to determine the shrinkage of a used brush (and the loss of fiber strikes) is often determined by measuring the width of the cleaning brush nip(s) to the photoreceptor. The nip width was manually measured directly from the photoreceptor surface or from a tape transfer that provided a permanent record of the testing conditions when the brush diameter was known. A simple equation relates the nip width to the brush diameter and the interference, (1/2 Dia.).sup.2 =(1/2 Dia.-BPI).sup.2 +(1/2 Nip Width).sup.2. Unfortunately, the present procedure for measuring the nip width procedure is too dirty and complicated for use as a field service procedure.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,450,186 to Lundy discloses a flexible cleaner brush belt that increases brush belt life by flexing away from the photoreceptor when not in use. The flexible belt is lifted away from contact with the photoreceptor and placed back into contact with the photoreceptor by a camming device. A camming device attached to linkages, increases the diameter of the flexible brush belt to lift the brush belt away from contact with the imaging surface. The camming device urges the belt brush back into contact with the imaging surface by decreasing the diameter of the brush belt. This movement of the brush belt increases the brush belt life and does not cause print quality defects, excessive toner clouding, or loss of machine productivity.
U.S. Pat. No. 5,381,218 to Lundy discloses a conductive flexible cleaner brush belt having a plurality of detoning stations to remove particles from the brush fibers. At least one of the rollers about which the flexible belt brush is mounted has a small diameter for spreading the brush fibers apart. This spreading of the fibers creates a node affect as the fibers rebound, adjacent fibers open creating a moving node affect. This node affect facilitates detoning of the brush by an air vacuum as air removes the particles from the brush fibers.